The earliest you can take a test is 5 days before so if you're due 1st May then you could take it today - but the earliest you take a test the least reliable the result would be (you could get a false negative) because the preganancy hormone (HCG) is only tiny amounts at that point.

Statistically I'd say it's low chance you'd be pregnant but any time you have intercourse (even with protection no method is 100%) there's statistically a chance.